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Ms. Katie Hower GHOMATPlx <br /> Chevron Environmental Management Company <br /> March 29, 2000 <br /> Page 3 <br /> Specific comment number 5 - "The grab groundwater sample was not analyzed for TPHgas <br /> or diesel yet it was analyzed jar BTEX and PARS. Please explain the logic of this decision." <br /> Response: The subject water sample was collected for human health risk assessment (HRA) <br /> purposes only; the TPH measurement is not used in the HRA. <br /> Specific comment number 6- "Geomatrix uses the environmental data from Earth Systems <br /> Consultants in the risk assessment yet the data is nor provided in the data summaryprovided <br /> in Appendix B. If the data are tabs used in the risk assessment, copies should be included in <br /> the Appendix for HERD's review. The Earth Systems data are clearly the highest reported <br /> detections at the property." <br /> Response: While we used Earth Systems Consultants' analytical results (concentrations)in <br /> our HRA, Geomatrix does not include analytical laboratory reports (laboratory sheets) <br /> generated by other consultants in our reports. We have attached a copy of the Earth Systems <br /> Consultants reports,which include their analytical laboratory sheets,to this document for <br /> your review. <br /> Specific comment number 7- "HERD reproduced the risk calculations. The hazard index <br /> was less than 0.4 and the theoretical excess cancer risk was approximately I x 10. Both of <br /> these risk levels are at or below acceptable risk ranges." <br /> Response: No response required. <br /> If you have any questions or require additional information,please call either of the <br /> undersigned. <br /> Sincerely, /�//// <br /> GEOMATRIX CONSULTANTS,INC. 4 <br /> ��, lG <br /> Michael R Keim Dawn h Zemo, C.E.G. <br /> Project Scientist Principal drogeologi <br /> MMDAV, <br /> \\S6\dep,Eaza\Dac_Safe\6000s\6�IS 019\Pombo\P.Respome-Lo- <br />